One of the well-known modules is a semiconductor light source module that ensures that the laser beam emitted from a semiconductor laser is converged through a light converging optical system onto the end surface of an element such as an optical fiber and SHG element forming an optical transmission line. Since the aperture of an optical waveguide of a SHG element has a diameter (the diagonal length for a rectangular aperture) on the order of several μm, positioning the semiconductor laser, light converging optical system and SHG element mutually with high-precision is essential to improve the light use efficiency of the light to be converged as a spot light with high accuracy. However, even if these components are firmly fixed at the time of assembling, mutual positional relationship may deviate in response to the temperature change and other environmental change.
Japanese Non-Examined Patent Publication 1991-223727 (TOKUKAIHEI 3-223727) discloses the technique wherein a wavelength conversion element and a laser beam source are connected using a lens barrel whose thermal expansion coefficient is equal or approximate to the wavelength conversion element, whereby the influence of the temperature change is restricted. Further, Japanese Non-Examined Patent Publication 2003-338795 (TOKUKAI 2003-338795) describes the technique wherein, when a laser beam emitted from the semiconductor laser is converged onto the end surface of an optical transmission element through a light converging optical system, the light reflected from the end surface or the light passing through the optical transmission element is detected, and then, the light converging optical system is driven in the direction perpendicular to the optical axis, whereby the spot light is adequately converged onto the end surface of the optical transmission element.
However, in the Japanese Non-Examined Patent Publication 1991-223727, it is difficult to eliminate the effect of the temperature variation completely even by using a lens barrel whose thermal expansion coefficient is equal or approximate to the wavelength conversion element. Further, when a humidity variation, vibration or other factors has occurred, deviation in the positional relationship among the semiconductor laser, light converging optical system and SHG element may be caused. Further, in Japanese Non-Examined Patent Publication 2003-338795, the light converging optical system is driven to perform positioning by detection of the light reflected from the end surface or the light inside of the optical transmission element. It is difficult to apply this method to an element requiring high-precision positioning such as a SHG element. To be more specific, there is a possibility that the light reflected from the end surface may not be detected accurately when a figure tolerance of the end surface is not excellent, therefore, detecting light inside of SHG element may cause any trouble over wavelength conversion of a light flux which is primary function of the SHG element, in addition to the high-precision positioning.